In some cases, an ailment or medical condition may affect the quality of a patient's sleep. For example, neurological disorders may cause a patient to have difficulty falling asleep, and may disturb the patient's sleep, e.g., cause the patient to wake frequently during the night and/or early in the morning. Further, neurological disorders may cause the patient to have difficulty achieving deep sleep stages, such as one or more of the nonrapid eye movement (NREM) sleep stages.
Examples of neurological disorders that may negatively affect patient sleep quality include movement disorders, such as tremor, Parkinson's disease, multiple sclerosis, or spasticity. The uncontrolled movements associated with such movement disorders may cause a patient to have difficulty falling asleep, disturb the patient's sleep, or cause the patient to have difficulty achieving deep sleep stages. Parkinson's disease may also cause rapid eye movement (sleep) behavior disorders (RBD), in which case, a patient may act out dramatic and/or violent dreams, shout or make other noises (e.g., grunting) during the rapid eye movement (REM) stage sleep.
Drugs are often used to treat neurological disorders. In some cases, neurological disorders are treated via an implantable medical device (IMD), such as an implantable stimulator or drug delivery device. The treatments for neurological disorders may themselves affect sleep quality. Further, in some cases, poor sleep quality may increase the symptoms experienced by a patient. For example, poor sleep quality may result in increased movement disorder symptoms in movement disorder patients. The link between poor sleep quality and increased symptoms is not limited to ailments that negatively impact sleep quality, such as those listed above. Nonetheless, the condition of a patient with such an ailment may progressively worsen when symptoms disturb sleep quality, which may, in turn, increase the frequency and/or intensity of symptoms of the patient's condition.